Crossing experiments with Enteromorpha intestinalis and E. compressa from different European localities

Sexual compatibility in the marine algae Enteromorpha intestinalis and E. compressa has been studied using laboratory cultures from various geographical areas in Europe. The two species are found to be totally separated by a sterility barrier. Well branched plants always fall in the same of the two genetically isolated groups and should be called E. compressa s.str., while most other plants should be referred to E. intestinalis s.l. The early development of sporophyte germlings may follow two different patterns, both of which have been observed in a single combination of parental plants, though not at the same time.